Displays incorporated in small devices, such as mobile devices, employ p-Si (polysilicon) for manufacturing thin film transistors (TFTs) for reasons such as reducing power consumption. At present, the manufacturing of p-Si TFT flat panel displays requires a heat treatment at relatively high temperatures of 400-600° C. Glass with excellent heat resistance is used for glass substrates for manufacturing p-Si TFT flat panel displays. It is known, however, that glass substrates used for conventional a-Si (amorphous silicon) TFT flat panel displays do not have sufficiently high strain points, and thus, significant heat shrinkage occurs due to the heat treatment at the time of manufacturing p-Si TFT flat panel displays, thus giving rise to the problem of uneven pixel pitch.
In recent years, a higher degree of definition is demanded of displays for small devices. Thus, it is desired to minimize unevenness in pixel pitch, and the inhibition of heat shrinkage of the glass substrate at the time of manufacturing displays, which is a cause of unevenness in pixel pitch, has been an issue.
The heat shrinkage of a glass substrate can generally be inhibited by increasing characteristic temperatures in the low-temperature-viscosity range (referred to hereinafter as “low-temperature-viscosity characteristic temperatures”), typified by the strain point and Tg (glass transition point) of the glass substrate. As an example of glass having a high strain point, Patent Literature 1 discloses a non-alkali glass having a strain point of 680° C. or higher.    Patent Literature 1: Japanese Patent Application Laid-Open Publication JP-A-2010-6649